Immanuel Kant is one of the most prominent western philosophers, and arguably the most influencial voice of the period in history known as "the Enlightenment". Kant defined his era as a time where autonomous thinking was urgent, and contended that only trough questioning external authority, can one expect to reach knowledge that is true, i.e. unbiased. The categorical imperative is one of his most famous concepts, and it amounts to a self-directed personal struggle that each human has to face while trying to follow the path of righteousness and morals; such path is not static, but rather an utterly dynamic path.
Kant's major criticism of previous ethical theories aims toward their lack of consideration for the inseparable duality which supports to the human condition, which manifest in the contrast between sensible and intellectual faculties; in fact, he recognized his own inability to develop a universal standard of ethics that would encourage autonomous thinking; as a result, he entered a hiatus which lasted for more than one decade.
After that long period of reflection, he published "The Critique of Pure Reason", a book that would turn out to be a major landmark in the western philosophical thought. (wiki) At this point, he advocated that knowledge is not external to the mind, but quite the opposite: that mind is necessarily a part of knowledge, its contribution transcendental, and not merely psychological: we define reality in the same measure that reality defines us.
His conception implies that morality should be rooted on the common principle of individual freedom, and that each individual is in turn responsible for his own morality. All principles of ethics can be inferred from the maxims that support each action, and each maxim must result from categorical imperative, which is the like a golden rule; every action that is...